1. Field of the Invention
The present invention relates to a process of production of a water-treating agent, in particular, relates to preparation of a grafted polyacrylamide flocculent containing cationic/ampholytic ions.
2. Description of the Related Art
Currently, with the development of environmental protection, requirement of water-treating agent becomes more and more urgent, and polyacrylamide is the most widely applied synthetic polymeric flocculant at present. But the production cost of polyacrylamide is relatively high. Therefore, the relevant professionals seek various approaches to lower cost and improve product performance. In particular, more attention is paid to cationic polyacrylamide, which is produced by copolymerizing a cationic monomer with acrylamide. For manufacturers in China the cationic monomer must be imported. Hence, development of a cationic flocculant with low cost of production, good performance and wide applicability is of real significance. Investigators, both domestic and abroad, paid attention to exploitative research of grafted polyacrylamide. In 80's decade, Chinese researchers succeeded in grafting acrylamide on to starch with cheap potassium permanganate instead of tetravalent cerium salt as initiator, and achieved high grafting efficiency and high degree of polymerization. It is a long step taken by acrylamide grafting technique toward industrial production. Due to the present of hydroxyl and amide functional groups and branched structure, the acrylamide grafted carbohydrate like starch has better flocculating effect than polyacrylamide under certain conditions, and further modifications may be made to give various derivatives to widen scope of application. No report on cationic modification of grafted polyacrylamide is found up to now. Domestically, though there is someone studied cationic modification of grafted polyacrylamide, but all carried out by direct reaction of formaldehyde with dimethylamine through classical Mannish reaction, which often results in crosslinking and product instability. Furthermore, a polyacrylamide with single cations in its structure is limited in application as a flocculating agent sometimes it must be used in combination with an anionic type polymeric flocculant, and thereby increasing trouble in operation. Additionally, owing to viscoelasticity, with increase of concentration, the mechanical load of stirring increased rapidly, which results in that the reaction is hard to control, and the product is also difficult to be diluted in use.